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Mathematics

x4+1x42x^4 + \dfrac{1}{x^4} - 2 in the form of factors is :

  1. (x1x)2(x+1x+1)2\Big(x - \dfrac{1}{x}\Big)^2\Big(x + \dfrac{1}{x} + 1\Big)^2

  2. (x1x)2(x+1x)2\Big(x - \dfrac{1}{x}\Big)^2\Big(x + \dfrac{1}{x}\Big)^2

  3. (x+1x)2(x1x+1)2\Big(x + \dfrac{1}{x}\Big)^2\Big(x - \dfrac{1}{x} + 1\Big)^2

  4. (x+1x)2(x+1x1)2\Big(x + \dfrac{1}{x}\Big)^2\Big(x + \dfrac{1}{x} - 1\Big)^2

Factorisation

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Answer

Given,

=x4+1x42=(x2)2+(1x2)22×x2×1x2=(x21x2)2=[(x1x)(x+1x)]2=(x1x)2(x+1x)2.\phantom{=}x^4 + \dfrac{1}{x^4} - 2 \\[1em] = (x^2)^2 + \Big(\dfrac{1}{x^2}\Big)^2 - 2 \times x^2 \times \dfrac{1}{x^2} \\[1em] = \Big(x^2 - \dfrac{1}{x^2}\Big)^2 \\[1em] = \Big[\Big(x - \dfrac{1}{x}\Big)\Big(x + \dfrac{1}{x}\Big)\Big]^2 \\[1em] = \Big(x - \dfrac{1}{x}\Big)^2\Big(x + \dfrac{1}{x}\Big)^2.

Hence, Option 2 is the correct option.

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